Washington — In his first hearing before the House Armed Services Committee, new US Cyber Command head Gen. Keith Alexander offered a troubling window into the threats that Pentagon networks face at the hands of terrorist and criminal syndicates, foreign intelligence organizations, and “hacktivists” intent on infiltrating power grids and financial networks.

These are threats that could hamper the US war effort in Afghanistan. Though the command recently deployed an “expeditionary cybersupport” unit to help to defend US networks in Afghanistan, Alexander on Thursday told the committee: “We’re not where we need to be” in ensuring the security of US military networks there.

In the past, cyberattackers have been able to steal key information from the US troops who rely on sophisticated equipment, including data on convoy supply routes, according to senior US officials.

Every hour, there are some 250,000 attempted attacks on Defense Department networks worldwide, Alexander told the committee. Throughout the Department of Defense, there are more than 15,000 different computer networks, including 7 million computers on some 4,000 military installations, committee chairman Rep. Ike Skelton (D) of Missouri pointed out.

“How are we going to defend this network in crisis?” Alexander, for his part, wondered aloud.

That was the question of the day, and Alexander, who also serves as the head of the National Security Agency, candidly admitted that his command continues to struggle for answers.

Citing some of the most startling breaches of security, Alexander pointed to “hacktivists” who have recently made it “nearly impossible for banks to do business” in targeted attacks on financial networks.

He also said that in the event of an offensive against the US power grid – a looming threat often cited by cybersecurity experts – defenses would have to rely on the private commercial sector rather than the Pentagon, Alexander said. Cyber Command’s mission is currently limited to defending Defense Department networks.

“It is not my mission to defend, today, the entire nation." Nor could he, Alexander added.

Pinpointing the source of the attack is equally problematic. That capability “is difficult – and not something we have."

Still, Alexander said he would continue to try, particularly in Afghanistan, where the expeditionary cybersupport unit is now in place to support the commander of US and NATO forces there, Gen. David Petraeus.

Added Alexander in one of the hearing’s rare moments of levity, “I did not want him to beat me up for not doing that.”